1. Field of the Invention
This invention relates to a process for alkylating wax to liquid materials boiling primarily in the lube oil range. More particularly, this invention relates to a process for alkylating waxy, normally solid hydrocarbons to liquid hydrocarbons boiling primarily in the lube oil range, by contacting the wax and a low molecular weight olefin, such as ethylene, with a catalyst comprising one or more C.sub.3 -C.sub.5 carbon atom secondary alcohols at elevated temperature and pressure.
2. Description of the Prior Art
It is well known in the art to dewax wax-containing mineral oils, particularly the lube oil fractions of petroleum oils, in order to remove at least a portion of the wax therefrom to obtain a dewaxed oil of reduced pour point. For many years this wax has been removed via various solvent dewaxing processes. In solvent dewaxing processes, the temperature of the wax-containing oil is lowered sufficiently to precipitate the wax therefrom as solid crystals of wax. At the same time, solvents are added to the waxy oils in order to improve the fluidity and reduce the viscosity thereof so that various filtration processes can be used to separate the wax from the dewaxed oil. Generally, the wax filtration temperature must be around 10.degree. or 20.degree. F. lower than the pour point requirement of the dewaxed oil due to a phenomenon known as pour-filter temperature inversion.
More recently, it has been found that certain zeolite type materials such as the hydrogen form of mordenite, commonly referred to in the art as decationized or H-mordenite, and certain ZSM-type crystalline aluminosilicates are effective in catalytically dewaxing petroleum oil fractions such as lube oil fractions. Thus, U.S. Pat. Nos. 3,516,925 and 3,539,498 disclose catalytically dewaxing lube oil fractions over a hydrogen form of mordenite, while U.S. Pat. No. 3,700,585 discloses the use of crystalline aluminosilicates of the ZSM-5 and ZSM-8 types for catalytically dewaxing hydrocarbon fractions such as jet fuels and lube oil fractions. These catalytic dewaxing processes are particularly useful for producing lube oils of especially low pour point which is required for certain specialty applications such as transformer oils, refrigerator oils and aviation turbine oils. However, disadvantages associated with these catalytic dewaxing processes include the fact that significant quantities of hydrogen are consumed by the process, which hydrogen must be added to the reaction zone and the wax is cracked down into low molecular weight fractions which are normally gaseous at room temperature and atmospheric pressure. Thus, these processes consume significant quantities of hydrogen and convert the wax to relatively non-valuable, gaseous by-products. Further, these catalysts are susceptible to poisoning and the VI of the catalytically dewaxed oil is substantially lower than that of the feed. It would be of value if one could catalytically dewax lube oil fractions and, at the same time, convert the wax into useful lube oil products. Further, it would be advantageous to be able to convert petroleum waxes in general to useful lube oil products.
One such process was disclosed in U.S. Pat. No. 2,741,649 which relates to a process for forming lubricating oils from waxy, normally solid hydrocarbons via an alkylation reaction comprising reacting the wax with a low molecular weight olefin such as ethylene in the presence of halogen-containing catalysts such as chloroform to produce useful lube oil products from the wax. However, introduction of halogens into a process (even if these halogens are present in halogen-containing hydrocarbons such as chloroform), results in severe corrosion problems in refinery processing equipment and if residual halogen-containing material remains in the product, this can cause severe corrosion problems in service. Hence, processes using such halogen-containing catalysts are undesirable from the standpoint of both processing and product quality.
Isomerization using noble metal catalysts has been found to be somewhat effective with refined waxes, but not with waxes in the presence of oil. Therefore, it would be desirable to provide a catalytic dewaxing process that possesses the required degree of selectivity for converting waxy molecules into lubricating oil components in the presence of oil molecules without generating or introducing corrosive materials into either the processing equipment or product.